3.9 rebuild pistons 8.13 9.35

[theg]

when rebuilding a 3.9 low comp motor can I buy 9.35 pistons and fit them . What is the physical difference between them . Is the dish smaller . Anyone got pics of the 2 pistons ?

[MacMan]

I didn't actually do a side-by-side comparison of my old 8.13s and the soon to be installed 9.35s but I imagine the only difference is the dishing. No other way it could be done because they still have to work with the same deck height. Everything is sitting in town while the machinist does my flanged liners but I should be able to give you a photo in a week or so.

[theg]

I didn't actually do a side-by-side comparison of my old 8.13s and the soon to be installed 9.35s but I imagine the only difference is the dishing. No other way it could be done because they still have to work with the same deck height. Everything is sitting in town while the machinist does my flanged liners but I should be able to give you a photo in a week or so.

thanks mate .
Im about to have my block decked just to true up the surfaces and also wonder how much can be decked off the block and heads before the intake will need machining ? Probably should have another thread for this question !

[400HPONGAS]

Just How Far Down the Hole is the piston(s) at TDC anyway ?
Any head decking or Block decking theoretically requires Multiplying what you took off by the Square root of 2 for a 90 degree V
Square root of 2 = 1.414
Therefore .040 off = .056 of inlet manifold face Distance or .028 a side.

And while your there , if rod length is 5.660 and Deck height is 8.96 amd Piston CR is 1.94 and stroke is 2.8
Then half the stroke 1.4 plus the rod length 5.66 plus the piston CR 1.94= 9 which is bit strange ,seeing nominal block height is supposed to be 8.96
so that would mean its out of the hole by .040 . Ive definately got one of those numbers wrong !!!
Anyone know the correct
Block Height
Piston Center line to Crown
Stroke
Rod Length CL

[p38arover]

When my engine was rebuilt, I had HC pistons fitted vice the original LC.

[DiscoVan]

You can use ford 255 pistons+30thou.

[Dougal]

When my engine was rebuilt, I had HC pistons fitted vice the original LC.

Did it make much difference (other than being rebuilt)?

[p38arover]

Did it make much difference (other than being rebuilt)?

Hard to say, Dougal. It had a full balance, ports matched, top-hat liners, high compression pistons, stage 2 cam, LPG injection, Haltech Interceptor, etc. Probably made a small difference. :(